In Patent Literature 1, there is described a heat exchanger including a windward tube row, a leeward tube row, and fins. The windward tube row and the leeward tube row are each constructed by a plurality of flat tubes arranged in parallel, and are arrayed in a flow direction of air. The fins are joined to the flat tubes. The heat exchanger includes a connection unit including n number of communication paths for allowing end portions of n number (n is an integer of 2 or more) of flat tubes constructing the windward tube row and end portions of n number of flat tubes constructing the leeward tube row to communicate with each other, respectively. The connection unit includes a second windward header collection pipe, a second leeward header collection pipe, and n number of coupling pipes. An internal space of the second windward header collection pipe is partitioned by a large number of partition plates into n number of first coupling spaces that communicate with the end portions of the n number of flat tubes constructing the windward tube row, respectively. An internal space of the second leeward header collection pipe is partitioned by a large number of partition plates into n number of second coupling spaces that communicate with the end portions of the n number of flat tubes constructing the leeward tube row, respectively. The n number of first coupling spaces and the n number of second coupling spaces communicate with each other by the n number of coupling pipes, respectively.